#include<stdio.h>
int main()
{
	int h1,h2;
	int a,b;
	scanf("%d%d",&h1,&h2);
	a=h1/100*60+h1%100;
	b=h2/100*60+h2%100;
	int cha=b-a;
	int x=cha/60;
	int y=cha%60;
	printf("%02d:%02d",x,y);
	return 0;
 } 
